##submission.abstract##
Background: The foramen magnum is an important anatomical landmark situated in the occipital bone at the base of the skull. It transmits the lower medulla, meninges, vertebral arteries, spinal accessory nerves, anterior and posterior spinal arteries, and venous plexus. Morphometric evaluation of the foramen magnum is useful in anatomy, anthropology, forensic identification, radiology, neurosurgery, and craniovertebral junction procedures.
Aim: To study the morphometry and shape variations of the foramen magnum in adult human dry skulls and to assess its anatomical and clinical significance.
Materials and Methods: A descriptive observational study was conducted in the Department of Anatomy using 80 adult human dry skulls of unknown sex. Skulls with damaged occipital bone, broken margins of the foramen magnum, deformity, or gross pathology were excluded. Anteroposterior diameter, transverse diameter, and foramen magnum index were measured using a digital Vernier caliper. The shape of the foramen magnum was classified as oval, round, tetragonal, hexagonal, irregular, or egg-shaped. Data were analyzed using descriptive statistics.
Results: The mean anteroposterior diameter of the foramen magnum was 34.82 ± 2.46 mm, while the mean transverse diameter was 29.76 ± 2.18 mm. The mean foramen magnum index was 85.52 ± 5.74. Oval shape was the most common type, observed in 32.5% skulls, followed by round shape in 21.3%, tetragonal shape in 16.3%, hexagonal shape in 12.5%, irregular shape in 10.0%, and egg-shaped foramen magnum in 7.5%. The anteroposterior diameter was greater than the transverse diameter in most skulls.
Conclusion: The foramen magnum shows considerable variation in dimensions and shape. Morphometric knowledge of the foramen magnum is important for neurosurgical approaches to the craniovertebral junction, radiological interpretation, forensic anthropology, and anatomical teaching. The data generated may serve as a regional reference for anatomical and clinical applications.